Axios

Much of the U.S. is under siege from extreme weather.

The big picture: Heat warnings and watches are in effect for over 100 million people as a record-breaking heat wave sweeping the southern U.S. continues to expand. Meanwhile, air quality alerts have been issued for an estimated 80 million others as wildfire smoke from Canada chokes much of the Mid-Atlantic, Midwest, Ohio Valley and even the Southeast.

Americans aren't fully supportive of backing away from fossil fuels and are not yet sold on an all-electric vehicle future after 2035.

The big picture: Those findings are part of detailed new Pew Research Center polling. At the same time, the data shows a large majority of those surveyed favor taking steps to combat climate change and prioritizing renewable sources like solar and wind power.

Firefighters in Canada are now battling 497 active wildfires across the country after 31 new blazes ignited, according to the latest data from the Canadian Interagency Forest Fire Centre.

The big picture: New figures show 3,023 fires have burned across some 19.7 million acres of land during what officials this week declared has been Canada's worst wildfire season on record.

Smoke from unprecedented wildfires in Canada triggered poor air quality alerts over swaths of the U.S. again on Wednesday, with multiple cities reporting some of the worst air pollution levels of any major city around the world.

The latest: While continuing to choke the Great Lakes region and the upper Midwest Wednesday, the low-lying smoke also drifted southeast and began affecting Ohio Valley and Mid-Atlantic cities.

Heat-related emergency room visits are spiking in Texas, as forecasters warn the dangerously high temperatures will continue to expand into the Lower Mississippi Valley and Mid-South through Thursday.

State of play: Texas saw an average of 837 heat-related emergency department visits per 100,000 from June 18-24 amid ongoing triple-digit temperatures in the record heat wave that's now in its third week — up from 639 visits per 100,000 ER visits for the same period last year, per the CDC.

First, the record Canadian wildfire season exposed residents of the biggest cities in the Northeast and mid-Atlantic to hazardous air quality. Now low-level smoke is taking aim at the Midwest and Ohio Valley.

Why it matters: Wildfire smoke is a public health hazard that can aggravate chronic conditions and pose risks for even healthy populations.

Hundreds of sea lions and dolphins are washing up dead or sick on California beaches due to a toxic offshore algae blooms, officials warn.

Driving the news: The Marine Mammal Care Center, which serves Los Angeles County, is at full capacity as the nonprofit rescue organization responds to "an unprecedented number of animals" falling ill to a neurotoxin from the bloom, CEO John Warner said at a news conference Tuesday.